Power drive transmission assembly

ABSTRACT

A power driven transmission assembly for an internal combustion engine, which assembly includes an endless V-belt that extends between a driving and a driven pulley. The driven pulley is subject to varying loads. The driving and driven pulleys each include first half portions which are transversely movable relative to the first half portions. By concurrently moving the second half portions relative to the first half portions, the effective pitch diameters of the driving and driven pulleys relative to the belt is varied for the transmission assembly to automatically deliver rotational power that in magnitude is related to a desired degree to the torque curve or torque capability of the prime mover with which the invention is associated. The effective pitch diameter ratio of the pulley system is changed by varying the pitch diameter of the driving pulley by power means. The power means is energized and is responsive to an electro mechanical servomechanism that senses the rate of rotation of the driving pulley and the lateral position of the second portion thereof relative to the first portion. By comparing the two signals, the second pulley portion of the driving pulley is moved laterally to a position where the driven pulley is delivering rotational power at a desired relationship to the torque curve of the engine. Radial balance is maintained throughout the shifting pattern as the effective pitch diameters of the driving and driven pulleys changes, for there is no radially moving parts in the present invention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Power drive transmission assembly.

2. Description of the Prior Art

In the past, various power operated assemblies have been proposed andused in an attempt to automatically control the pitch diameter ratios ofa driving and driven pulley connected by a V-belt in accordance with therate of rotation imposed on one of the pulleys. Such prior art deviceshave, in the main, utilized centrifugal means to attempt to accomplishthis result, but such centrifugal means are effective in but a limitedrange, and have the disadvantage that they impart a radial imbalance tothe system.

The primary purpose in devising the present invention is to supply apower drive transmission assembly which can be automatically or manuallycontrolled to provide a desired pitch diameter ratio to the driving anddriven pulleys engaged by an endless V-belt. This ratio is achieved byvarying the pitch diameter of the driving pulley only, and the pitchdiameter of the driven pulley automatically varying in accordancetherewith due to the spring loaded structure of the driven pulley. Thechange of the effective pitch diameter of the driving pulley only isaccomplished by moving a second portion thereof relative to a firstportion, which increases or decreases the pitch diameter of the drivingpulley. The pitch diameter of the driven pulley is also controlled bythe belt tension, and the magnitude of the spring loading on the secondhalf portion of the driven pulley.

A major object of the present invention is to provide a powertransmission assembly for a prime mover, such as an internal combustionengine, which assembly may be so adjusted that a driving pulley, drivenpulley and connecting V-belt that form a part thereof are so controlledand so cooperate with power means and a sensing device that detect boththe rate of rotation and the lateral position of a second movable halfportion of the driving pulley relative to a half portion that rotates ina fixed position on the driving shaft, that the power means is energizedto vary the lateral spacing between the first and second half portionsof the driving pulley that a desired pitch diameter ratio is achievedbetween the driving and driven pulleys. As the lateral spacing betweenthe first and second half portions of the driving pulley is varied, thetension on the V-belt is increased or decreased, and the effectivediameter of the driven pulley is varied by laterally moving a secondspring loaded second portion thereof relative to a first portion of thedriven pulley that is rigidly secured to the driven shaft, with theratio between the pitch diameter of the driving and driven pulleys whenthe invention is operating at all times has a desired relationship tothe torque curve of the prime mover.

Another object of the invention is to supply a power transmissionassembly that when in operation effects an infinite number of variationsin the effective pitch dimeter ratio of the driving and driven pulleyswithout loss of power, is at all times in radial balance, requires noradially movable parts or weights and in effect uniformly shifting thepitch diameter ratio of the driving and driven pulleys without beingdependent on the rate of rotation of the driving pulley.

A further object of the invention is to supply a power transmissionassembly that is easily and conveniently adjusted to a particular torquecurve of a particular engine or prime mover, and when so adjusted willcontinue to automatically have a desired relationship to the torquecurve of the engine as the driven pulley is subjected to varying loads.

Another object of the present invention is to supply a power drivetransmission that has a broad capability to accept a wide variation ofengine drive speeds, horse power, and torque output, and permit greaterefficiency to be obtained from the engine inasmuch as the power driveassembly does not require the capability to sense torque being appliedto the driven pulley.

Yet another object of the invention is to furnish a power transmissionassembly that permits upward and downward shifting of the pitch diameterratios of the driving and driven pulleys without the driving force beingdisengaged therefrom.

SUMMARY OF THE INVENTION

The power drive transmission assembly is used in conjunction with aprime mover, such as an internal combustion engine or electric motor,that has a known torque curve. The engine is provided with a drivingpulley that includes a first half portion that rotates in a fixedposition relative to the drive shaft of the engine. The driving pulleyincludes a second half portion that may move laterally to the first halfportion on the driven shaft. Power means are provided that effectcontrolled lateral movement of the second half portion of the drivingpulley relative to the first half portion thereof.

The driving pulley is engaged by an endless V-belt, which belt alsoengages a driven pulley that is subject to a load of varying magnitude.The driven pulley includes a first half portion that rotates in a fixedposition on the driven shaft, and a second half portion that is springloaded and at all times tends to move toward the first half portion ofthe driven pulley.

The power driven transmission assembly includes an endless rotatablesurface that rotates with the driving pulley. The endless surface has asequence of spaced light reflecting surfaces of generally triangularshape thereon that are constantly scanned by a photoelectric device. Thelight reflecting surfaces are of such shape that when scanned by thephotoelectric device first and second electric signals are generatedthat in magnitude are related to the rate at which the driving pulleyrotates and the position of the second half portion of the pulley.

The first and second signals are continuously compared by electronicmeans that at all times tend to maintain them in balance by actuatingthe power means to move the second portion of the driving pulleylaterally relative to the first half portions thereof. Such movement ofthe second half portion of the driving pulley changes the effectivepitch diameter of the driving pulley, and the magnitude of the tensionexerted on the belt. This change in tension on the belt results in theeffective pitch diameter of the driven pulley changing due to variationin the lateral force imposed on the spring loaded second half portion ofthe driven pulley. Thus, the power drive transmission assemblyconstantly changes the ratio of the effective pitch diameters of thedriving and driven pulleys to maintain the first and second electricsignals in balance. The spacing and configuration of the lightreflecting surfaces is so chosen that the first and second signals arein balance when the engine is operating to produce torque on the drivenpulley that has a desired relationship to the torque curve. The lightreflecting surfaces will normally be so chosen that the first and secondsignals are in balance when the engine is producing less than themaximum torque possible through the driving pulley, for otherwise itwould not be possible to accelerate the engine to drive the drivingpulley at a greater rate of rotation.

The power drive transmission assembly of the present invention has theadvantages over prior art devices of this nature in that the inventionprovides:

1. Greater variation in effective pitch diameter ratios between thedriving and driven pulleys;

2. Broader capability of accepting wide variations of engine drivespeed, horsepower and torque output;

3. Greater efficiency in that the invention does not require thecapability to sense torque applied to the driven shaft;

4. Automatic or manual up or down shifting of the effective pitchdiameter ratios without disengaging the drive force;

5. Is at all times in balance in that there is no radially movableparts.

6. Can be made to follow an electronically generated shifting pattern.

In another embodiment the objects of the present invention areaccomplished with the unique combination similar to that previouslydescribed. In the second embodiment the lateral movement of the secondhalf portion of the driving pulley relative to the first half portion isfixed by a manual control acting together with a feedback loop. Thefeedback loop comprises a load sensor which senses the load on the primemover and a automatic voltage level setting circuit. The automaticvoltage level setting circuit is coupled between the manual control andthe power means that move the second half portion of the driving pulley.The output of the load sensor is coupled to an input of the voltagelimiting circuit such that the maximum level of the voltage applied tothe power means is fixed by the load sensor.

In the second embodiment the prime mover rotates at a constantrotational speed and the effective pitch diameter ratio between thedriving and driven pulleys is primarily set by the manual control.Accordingly, even though the prime mover is operating at a constantrotational speed, the output rotational speed from the transmissionassembly may increase or decrease in response to the manual control solong as the load on the prime mover does not exceed some predeterminedset level. If the load on the prime mover exceeds the set level, thevoltage limiting circuit will reduce the voltage applied to the powermeans in response to the output of the load sensor to reduce theeffective pitch diameter ratio between the driving and driven pulleysthereby preventing the load on the prime mover from exceeding thepredetermined maximum load set by the load sensor.

In another embodiment of the present invention, the objects areaccomplished by a unique combination similar to that previouslydescribed except that the driving pulley and driven pulley areinterchanged in position. In other words, the driving pulley is utilizedas the driven pulley and the driven pulley is utilized as the drivingpulley. In the third embodiment, the prime mover is of the type whoserotational speed varies over wide ranges and it is desirable that theoutput of the power transmission be a constant rotational speed. In thisembodiment the position of the second half portion of the driving pulleyis controlled by a feedback loop. The feedback loop comprises a sensorwhich senses the rotational speed of the driven pulley and supplies anoutput to a comparator means which compares the output of the speedsensor with some reference signal which is related to the desiredrotational speed of the driven pulley. The comparator circuit generatesa signal to vary the effective pitch diameter ratio between the drivingand driven pulley which is applied to the power means on the drivenpulley so that the output signal from the speed sensor is equal to thereference signal.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and objects of the presentinvention will become more apparent by reference to the followingdescription taken in conjunction with the accompanying drawings, whereinlike reference numerals denote like elements, and in which:

FIG. 1 is a perspective view of an internal combustion engine in drivingarrangement with the power drive transmission assembly.

FIG. 2 is a longitudinal cross sectional view of a power drivetransmission assembly.

FIG. 3 is a fragmentary cross sectional view of a portion of theassembly within the oval defined by phantom line in FIG. 2 andidentified by the numeral 3, and illustrating the positioning of thepatterned light reflecting surface on a part of the driving pulley.

FIG. 4 is a top plan view of a sheet having patterned light reflectingstrips defined thereon, with each strip being adapted for use on theassembly to achieve a particular power output that is related to thetorque curve of the engine.

FIG. 5 in diagram form illustrates in conjunction with an endless V-beltthe effective pitch diameter ratios that may be achieved between adriving and driven pulley.

FIG. 6 is a top plan view illustrating the lateral shifting of portionsof the driving and driven pulleys.

FIG. 7 is a simplified top plan view of a second form of the invention.

FIG. 8 discloses plotted curves that illustrate the power output of theinvention relative to the torque curve.

FIG. 9 is a diagram illustrating the electrical circuit used on theinvention.

FIG. 10 is a top plan view of a third form of the invention.

FIG. 11 is an enlarged fragmentary cross-sectional view of the thirdform of the invention.

FIG. 12 is a perspective view of two of the components used in the thirdform of the invention.

FIG. 13 is a block diagram of a second embodiment of the inventionwherein the prime mover is a source of constant rotational speed.

FIG. 14 is a third embodiment of the present invention wherein an outputof constant rotational speed is desired.

FIG. 15 is a top plan view of a sheet having a pattern of lightreflecting strips defined thereon.

FIG. 16 is a cross-sectional schematic view of one embodiment of alinear actuator.

FIG. 17 is a simplified view taken along the lines 17--17 of FIG. 16.

DESCRIPTION OF THE PREFERRED EMBODIMENT

This application is a continuation in part of application for UnitedStates letters patent Ser. No. 525,450 filed Nov. 20, 1974.

An internal combustion engine C has a first form of power drivetransmission assembly D operatively associated therewith as shown inFIG. 1. Engine C and assembly D are illustrated in FIG. 1 as supportedon a base frame 10, which when the invention is used may be a part of avehicle chassis not shown.

Engine C as illustrated in FIG. 1 includes a drive shaft. In FIG. 2 adrive shaft 12 is illustrated that has a driving pulley F mountedthereon, and this pulley is capable of driving an endless V-belt 14.Driving pulley F is of split structure and includes a first half F-1that is by a key 16 rigidly secured to drive shaft 12. Drive shaft 12has a first grooved wheel 18 rigidly secured thereto. The first pulleyhalf F-1 is formed with an outwardly tapering interior first face 20 asmay best be seen in FIG. 2. Belt 14 has oppositely disposed side walls22 that taper inwardly toward one another at substantially the sameangle as that of the first face 20.

First pulley half F-1 as shown in FIG. 2 includes a cylindrical firsthub 24, with the first hub extending outwardly away from the firstsurface 20. First pulley F also includes a second half F-2, which secondhalf includes a second cylindrical hub 26 in which a longitudinal bore28 is formed. The bore 28 is slidably engaged by first hub 24. A key 30is secured to first hub 24 and slidably engages an interior groove 32 insecond hub 26 to prevent the first and second pulley halves F-1 and F-2rotating relative to one another as shown in FIG. 2. First half F-2 hasan outwardly tapering interior face 34, that tapers at substantially thesame angle as one of the belt side walls 22. The first and second faces20 and 34 taper outwardly away from one another as shown in FIG. 2. Bore28 on the inner end thereof develops into a recess 36 that is partiallydefined by a ring shaped body shoulder 38. A snap ring 40 is mounted ina circumferentiallly extending groove 42 formed on the outer surface offirst hub 24. The snap ring 42 serves as a stop when contacted by bodyshoulder 42 to limit the inward movement of second pulley half F-2relative to first half F-1. It should be understood that the assembly ofFIG. 2 may be employed with an assembly such as shown in FIG. 1 or otherassemblies. The common numbering and lettering between FIGS. 1 and 2 isonly suggestive of one possible form of cooperation.

A housing G is secured to engine C by bolts 44 or other suitablefastening means. Housing G has an outwardly disposed open end that isnormally closed by a first plate 46 that is removably secured thereto bybolts 48. First plate 46 has an opening 50 therein. A slot 52 is formedin the side of housing G as shown in FIG. 1. A second plate 54 isprovided that is disposed outwardly from first plate 46 and is removablysecured thereto by screws 57.

Returning to FIG. 2, the outer end of a second hub 26 has a circularmember 56 secured thereto by screws 58. A bore 60 is formed in thecenter of member 56. A rigid cylindrical shell 62 having an outwardlyextending flange 64 engages opening 50 and is gripped between first andsecond plates 46 and 54 when screws 57 are tightened as shown in FIG. 1.A block 66 is slidably supported in cylinder 62, with the block having apin 68 that extends outwardly therefrom to slidably engage alongitudinal slot 70 formed in the shell. A ball bearing assembly 72 isdisposed between member 56 and block 66. In FIG. 2 it will be seen thata compressed helical spring 74 is disposed in the open portion of thebore 28 and is in abutting contact with second pulley half F-2 andmember 56. Spring 74 at all times tends to move second pulley half F-2away from first pulley half F-1.

A threaded rod 76 is rotatably supported in a fixed longitudinalposition in second plate 54 as shown in FIG. 2, and rotatably engages atapped bore 78 formed in block 66. A grooved wheel 80 is secured to theoutwardly projecting end of rod 76 to permit the rotation thereof.Rotation of the rod 76 moves block 66, ring shaped member 56, ballbearing assembly 72 and second pulley half F-2 as a unit toward or awayfrom first pulley half F-1 dependent upon the direction of rotation ofthe rod 76.

An endless belt 82 as may be seen in FIG. 1 engages grooved wheel 80,with the belt extending to a grooved wheel 84 on the drive shaft of areversible electric motor 86, which motor is supported in a fixedposition relative to housing G by conventional means (not shown). Themotor 86, belt 82, grooved wheels 80 and 84 together with threaded rod76 and block 66 serve as a linear actuator to move the second pulleyhalf F-2 laterally relative to first pulley half F-1. The means by whichthe motor 86 is electrically energized will be explained later indetail.

The base 10 has bracket means 86 of conventional structure securedthereto as may be seen in FIG. 1, which bracket means rotatably supporta transversely disposed driven shaft 88. A driven pulley H is mounted onshaft 88 as shown in FIGS. 1 and 2, and is engaged by belt 14.

The driven pulley H includes a first half portion H-1 that is rigidlysecured to driven shaft 88 by a key 90. Key 90 engages a longitudinalslot 92 in driven shaft 88 and a slot 94 formed on the interior of acylindrical hub 96 that projects from first half H-1 as shown in FIG. 2.The driven pulley H includes a second half H-2 that has a cylindricalshell 98 projecting therefrom that is slidably mounted on a hub 96. Akey 100 engages aligned longitudinal grooves 102 and maintains the firstand second halves H-1 and H-2 in non-rotatable relationship relative toone another as shown in FIG. 2.

A compressed helical spring 104 encircles hub 98 and is in abuttingcontact with second half H-2 and a retainer 106 that is held in a fixedposition relative to driven shaft 88 by a resilient clip 108. The clip108 engages a circumferential groove 110 formed in the free end portionof hub 96 as may be seen in FIG. 2.

When the second half F-2 moves transversely relative to the second halfF-1, the tension and lateral force exerted by the belt 14 is varied toovercome the force exerted by the spring 104, with the effective pitchdiameter ratio between the driving pulley F and driven pulley H varyingbetween the extremes shown in FIG. 5. It will be particularly noted thatthe portions of the driving and driven pulleys F and H engaged by belt14 at all times remain axially aligned for as shown in FIG. 6, when thebelt 14 moves from a position shown in solid line to one shown inphantom line the lateral shifting of the second movable halves F-2 andH-2 is in the same direction. Thus, there is no tendency for belt 14 tobecome disengaged from the driving and driven pulleys as the effectivepitch ratios thereof is varied. Referring to FIG. 1 a grooved wheel 18(such as shown in FIG. 2) engages an endless belt 112 that drives agrooved wheel 114 secured to a rotatable shaft 116 of an electricalgenerator 118. The generator 118 is secured to a bracket 120 that isaffixed to the engine C by conventional means such as bolts 122 or thelike. Driven shaft 88 as may be seen in FIG. 1 has a power take offsprocket 124 mounted thereon that is engaged by a link belt 126 thatdelivers rotational power from engine C to a desired source.

The torque curve J of engine C is shown in FIG. 8 in solid line. Thetorque that is desired to be delivered by the driven shaft 88 fromengine C through transmission D by varying the pitch diameter ratios ofthe driving and driven pulleys F and H is indicated by the torque curveK in FIG. 1.

Horsepower is a product of torque and rotation speed, and the horsepowerat any given r.p.m. will vary directly with the torque. By selectivelyvarying the pitch diameter ratios of the driving and driven pulleys Fand H the torque curve K in the region thereof between 5500 and 10,500r.p.m. as shown in FIG. 8 can be made substantially flat.

The transmission D in combination with the automatic sensing device Lnow to be described permits the power output on the driven shaft 88 tofollow the torque cruve J to a desired degree, and obtain usable powerat the driven shaft in a more efficient manner than by manually varyingthe pitch diameter ratios of the driving and driven pulleys F and H.

A sheet M of pliable material, such as paper or the like is providedthat has a number of strips M-1 to M-4 inclusive defined thereon. Eachstrip M-1 to M-4 has a sequence of triangular shaped light deflectingareas N-1, N-2, N-3 and N-4 defined thereon and these areas beingseparated by dark non-light reflecting triangular areas 0-1, 0-2, 0-3and 0-4. The triangular areas N-1 to N-4 and 0-1 and 0-4 are ofdifferent configuration and widths for reasons that will later beexplained.

One of the strips M-1 to M-4 has light reflecting and non-lightreflecting areas of an appropriate configuration for engine C and ismounted on the hub 26 as shown in FIG. 2 to encircle the same.

The desired strip M-1 to M-4 is removably held in the encirclingposition on hub 26 by conventional means (not shown) such as an adhesiveor the like.

A source of electric energy is provided, such as a storage battery (notshown) which is charged when engine C is operating by the generator 118.Electric energy is delivered from generator 118 to the source throughconductors 130 shown in FIG. 1. The source of electric energy supplieselectric power V to a number of terminals that are identified in FIG. 9by the letter P.

A light emitting diode 132 is provided that directs a beam of light 134on the strip M-1 as it rotates with hub 26 as shown in FIG. 9. The diode132 is supported by a bracket 136 from shell 62 as shown in FIG. 2. Abeam of light 134' is reflected from the areas N-1 as they rotate to atransistor U that is electrically conductive only when the beamimpringes thereon.

One terminal of light emitting diode 132 is connected to a terminal P bya conductor Q and the other terminal by a conductor R to ground S. Apreamplifier 138, Schmidt trigger 140, monostable multivibrator 142 andlow pass filter 144 are connected by conductor 146, 148 and 150 as shownin FIG. 9. Transistor U, preamplifier 138, Schmidt trigger 140,monostable multivibrator 142 and low pass filter 144 each have oneterminal P and the other terminal by a conductor R to ground S.

The beam of light 134' is intermittent and as it intermittently renderstransistor U electrically conductive causes the latter to deliver apulsating voltage V to preamplifier 138. The frequency of the pulses ofvoltage V is related to the rate of rotation of the driving pulley F,and the time duration of each pulse is related to the time it takes foreach light reflecting area N-1 to rotate past the beam 134. The time ittakes for each light reflecting area N-1 to rotate past the beam 134 isrelated to the position of the second half F-2 of driving pulley Frelative to the first half F-1 thereof, for the light reflecting areasN-1 move laterally concurrently with the second half.

The pattern of the voltage V as it is altered by the elements 138, 140,142 and 144 is shown plotted against magnitude and time in small graphsadjacent the elements in FIG. 9, and the low pass filter delivering arelatively constant voltage B that in magnitude is related to the rateat which the driving pulley F rotates. Voltage B is delivered to aconductor 148.

A second low pass filter 154, inverter 156, summer 158 and power buffer160 are connected by conductors 162, 164 and 166 as shown in FIG. 9,with each of the above identified elements being connected to terminalsP and ground S by conductors Q and R.

Conductor 148 has a junction point 148a therein from which a conductor162 delivers electric energy in the squared voltage pattern V' to thesecond low pass filter 154. Inverter 156 delivers a voltage A to summer158 that is related to the time it takes for a light reflecting area N-1to move past beam 134 which in turn is related to the transversepositioning of the second half F-2 of driving pulley F relative to thefirst half thereof.

Power buffer 160 has a conductor 168 extending therefrom to a linearactuator X which when actuated is capable of transversely moving secondhalf F-2 of driving pulley F relative to first half F-1 to vary thepitch diameter of the driving pulley. The linear actuator X may beeither the first form X-1 thereof shown in FIG. 2 or a second form X-2illustrated in FIG. 7 and later to be described.

The voltages A and B due to inverter 156 are of different polarities.When voltages A and B are equal they cancel one another and power buffer160 is not actuated to energize the linear actuator X. The motive powerin actuator X-1 is the reversible motor 86. When voltages A and B arenot equal power buffer 160 causes a flow of electric current to motor 86through conductor 168 in a direction to cause the motor to rotatethreaded rod 76 in a direction to vary the pitch diameter of the drivingpulley F until A and B are again equal.

The width of the light reflecting areas N-1 is so chosen that the torqueJ of the driven shaft 88 will have a desired relationship to the torqueK of engine C. For instance, the segment K-1 of torque curve K as shownin FIG. 8 may be so selected that the effective pitch diameter ofdriving and driven pulleys F and H is 8 to 1, while the segment K-2 mayhave a pitch diameter of 2 to 1. In all instances it is desirable thattorque curve K be somewhat less than torque curve J to permitacceleration of the engine C.

From the foregoing discussion, it is apparent to one skilled in the artthat an electric motor could be substituted for internal combustionengine and that any sensor or combination of sensors which sense therotational speed of the prime mover and the position of the second halfportion of the driving pulley can be substituted for the light beamsensor described herein without departing from the spirit and scope ofthe present invention. Within this class of sensors or combinations ofsensors falls such devices as magnetic sensors, pneumatic sensors,hydraulic sensors and a sensor as simple as a cam follower coupled tothe wiper of a linear resistor.

In FIG. 7 a second form of the invention is shown in which the secondform X-2 of the linear actuator is used. Elements in the second form ofthe invention that are common to the first form are identified in FIG. 7by the same numerals and letters previously used but with primes beingadded thereto.

In the second form of the invention as shown in FIG. 7 plate 46' has afirst hydraulic cylinder 200 extending outwardly therefrom in which apiston 202 is slidably mounted that has a recessed inner portion 204 onwhich the ball bearing assembly 72' is mounted, with one race of theassembly secured to hub 26'. Hydraulic fluid Y may be discharged intoand out of first cylinder 200 through a passage 206.

Passage 206 is in communication with the outer interior portion of asecond hydraulic cylinder 208 that projects from plate 46'. A secondpiston 210 is slidably mounted in second cylinder 208. Second piston 210has a tapped cavity 212 therein that is engaged by a threaded shaft 214that is driven by a reversible electric motor 216. Electric motor 216rotates threaded shaft 214 when the motor is supplied with electricpower through conductor 168 and a conductor R in the manner previouslydescribed in connection with the first form of the invention.

When the motor 216 is actuated by electric power received from powerbuffer 160, the threaded shaft 214 is rotated to move second piston 210,with hydraulic fluid Y being forced into first cylinder 200 to movefirst piston 202 and second pulley half F'-2 relative to the firstpulley half F'-1 until the pitch ratios of the driving and drivenpulleys F' and H' is such that voltages A and B are equal. The abovedescribed operation will continue intermittently as the load on drivenshaft 88' varies, and as a result the torque delivered by driven shaft88' will follow the curve K illustrated in FIG. 8. Spring 74' tends atall times to move second half F'-2 away from first half F'-1.

In FIGS. 10 to 12 inclusive a third form of the invention is shown onwhich a third form X-3 of the linear actuator is used. Elements in thethird form of the invention that are common to the first form areidentified in FIGS. 10 to 12 by the same numerals and letters previouslyused but with double primes being added thereto.

In the third form of the invention as illustrated in FIGS. 10 to 12 abracket 300 secured to first plate 46" by bolts 302 serves as a fixedmounting for the outer cylindrical portion 304 of a hysteresis brake306. The hysteresis brake illustrated is manufactured commercially bythe Delevand Division, American Precision Industries, Inc., East Aurora,New York and serves as the third form of linear actuator X-3.

Brake 306 has coils 308 in portion 304 that may be electricallyenergized through conductors 168, Q and R. Brake 306 has a rotatableinner portion 310. Inner portion 310 is rotatably supported in outerportion 304 by a pair of spaced ball bearing assemblies 312. The innerportion 310 has a nut 314 on the outer end thereof that engages athreaded rod 316 that extends through a longitudinal bore 318 in theinner portion. Threaded rod 316 on a first end 316a thereof has a slot320 therein of rectangular transverse cross-section that is removablyengaged by an elongate cross-number 322 that is secured to circularmember 56" by a pin 324. Inner portion 310 has a circular recess 326therein that is engaged by a snap ring 328 that bears against the ballbearing assembly 312 nearest to the circular member 56". Snap ring 32limits the outward movement of inner portion 310 relative to outerportion 304 as may be seen in FIG. 10. Nut 314 is secured to innerportion 310 by conventional means (not shown).

When coils 308 are not electrically energized cross member 322 as itrotates causes concurrent rotation of inner portion 310, threaded rod316 and nut 314 as a unit. Upon coils 308 being electrically energizedby a signal received by the third form X-3 of the linear actuatorthrough conductor 168 the inner portion 310 is stopped from rotating,but the threaded rod 316 continues to rotate relative to the innerportion and nut 314. Rotation of threaded rod 316 relative to innerportion 310 results in lateral movement of second half F"-2 to firsthalf F"-1 of driving pulley F" to vary the effective pitch diameterthereof as previously described in connection with the first form of theinvention.

The use and operation of the invention has been described previously indetail and need not be repeated.

Furthermore, it should be apparent that linear actuator X may beimplemented in several other ways, such as, but not limited to ahydraulic or eddy current brake without departing from the spirit andscope of the invention.

Referring to FIG. 13, shown therein is another embodiment of the presentinvention. Elements in this embodiment of the present invention that arecommon to the other embodiments are identified in FIG. 14 by the samereference numerals.

Referring to FIG. 14, the embodiment shown therein includes a primemover represented by electric motor 400 having a drive shaft 12. Drivingpulley F which is substantially the same as the driving pulley Fpreviously described is mounted on drive shaft 12. Driving pulley F iscoupled to driven pulley H by V-belt 14. Driven pulley H issubstantially the same as the driven pulley H previously described.Linear actuator X is substantially the same as X-1 through X-3previously described is coupled to second pulley half F-2 of drivingpulley F. Position sensor 402 senses the position of second pulley F-2and the output of position sensor 402 is coupled to an input ofcomparator driver 404. The output of comparator driver circuit 404 iscoupled to linear actuator X.

Electric motor 400 is powered by a source of direct current representedby battery 406. Resistor 408 is coupled between the negative terminal ofbattery 406 and ground. The terminal formed by the negative terminal ofbattery 406 and one end of resistor 408 is coupled to an input ofvoltage limiting circuit 410 and the output of voltage limiting circuit410 is coupled to an input of comparator driver circuit 404.

Variable resistor 412 is coupled between a minus source of directcurrent voltage represented by a -V_(s) and ground and the wiper ofvariable resistor 412 is coupled to an input of voltage limiting circuit410. Pedal 414 is mechanically coupled to the wiper of variable resistor412 such that depressing pedal 414 causes the wiper of variable resistor412 to move such that the voltage between the wiper and ground increasesin magnitude toward -V_(s).

The voltage limiter circuit 410 comprises two operational amplifiers 416and 418. Resistor 420 is coupled between the input of operationalamplifier 416 and the connection formed by the negative terminal ofbattery 406 and one end of resistor 408. Capacitor 422 is coupledbetween the input and output of amplifier 416. Variable resistor 424 iscoupled between a positive source of direct current voltage representedby +V_(L) and ground. Resistor 426 is coupled between the wiper ofvariable resistor 424 and the input of operational amplifier 416. Theanode of diode 428 and the cathode of diode 430 are coupled to theoutput of amplifier 416. The cathode of diode 428 and the anode of diode430 are coupled respectively to one end of resistor 432 and ground. Theother end of resistor 432 is connected to the input of operationalamplifier 418. The two ends of resistor 434 are coupled between theinput of amplifier 418 and the wiper of variable resistor 412 andresistor 436 is coupled between the input and output of amplifier 418.The output of amplifier 418 is coupled to an input of comparator drivercircuit 404.

In practice, position sensor 402 can be substantially the same asautomatic sensing device L. Also, comparator driver circuit 404 can besubstantially the same as that portion of electronic circuit of FIG. 9comprising the series connection of preamp 138, Schmidt trigger 140, lowpass filter 154, inverter circuit 156, summer 158, and power buffer 160except that the output of voltage limiter circuit 410 is applied to aninput of summer 158 on conductor 152.

For the sake of illustration, assume that the output rotational speed ofelectric motor 400 is a constant and that the wiper contact of variableresistor 424 is set such that the voltage between the wiper contract andground is some positive value corresponding to a predetermined maximumload condition. Further, assume that pedal 414 is in a position suchthat the resistance between the wiper arm of variable resistor 412 andground is substantially 0 thereby making the input to amplifier 418substantially 0 volts. If pedal 414 is depressed, the wiper arm ofvariable resistor 412 is moved such that the voltage increases in anegative direction from 0 toward -V_(s) thereby causing the voltage atthe input of operational amplifier 418 to increase in the negativedirection. As the input voltage of amplifier 418 increases in thenegative direction the output voltage of amplifier 418 increases in thepositive direction and is coupled to the input of comparator drivercircuit 404. Comparator driver circuit 404 compares the signal fromposition sensor 402 with the output of amplifier 418 and if there is adifference applies a signal to linear actuator X to move second pulleyhalf F-2 relative to first pulley half F-1 until the difference betweenthe two signals is substantially 0. Accordingly, the effective pitchdiameter ratio between the driving and driven pulley is varied and theload on electric motor 400 increases.

As the load on electric motor 400 increases, the current supplied toelectric motor 400 by battery 406 increases thereby increasing thevoltage drop across resistor 408 in a negative direction. So long as thevoltage drop across resistor 408 is smaller in magnitude than thepositive voltage set by variable resistor 424, the output voltage of theintegrator formed by amplifier 416 and feedback capacitor 422 increasesin a negative direction. So long as the output voltage of amplifier 416is a negative, diode 428 is reverse biased effectively isolating theinput of amplifier 418 from the output of amplifier 416. Accordingly, solong as the output of amplifier 416 is negative, the output of amplifier418 will vary directly in proportion to movement of pedal 414. Toprevent the output of amplifier 416 from becoming too negative, diode430 coupled between the output and ground holds the output voltage at aminus one diode drop.

When the load current through resistor 408 reaches a point such that thevoltage drop across resistor 408 becomes greater than the voltage set onvariable resistor 424, the input voltage on amplifier 416 becomesincreasingly more negative thereby causing the output of amplifier 416to integrate toward a positive voltage. The increasing positive voltageat the output of amplifier 416 is reflected at the input of amplifier418 where it is additively combined with the negative voltagecorresponding to the voltage drop between the wiper of variable resistor412 and ground. Accordingly, the negative voltage appearing at the inputof amplifier 418 ceases to continue to increase in the negativedirection and the output voltage of amplifier 418 ceases to increase inthe positive direction as pedal 414 is depressed. Furthermore, so longas the load on electric motor 400 is in excess of some preselectedvalue, the output voltage of amplifier 418 will decrease, therebycausing linear actuator X to move the second pulley half F-2 relative tofirst pulley half F-1 to reduce the load on electric motor 400 therebyreducing the voltage drop across resistor 408 until the drop acrossresistor 408 equals the voltage preset on variable resistor 424. Whenthe voltage across resistor 408 and the voltage preset on variableresistor 424 are equal, the input voltage on amplifier 426 issubstantially 0 and the integrator formed by amplifier 416 and capacitor422 will cease to integrate up in a positive direction and hold theoutput voltage at some constant positive value. Similarly, if the loadon electric motor 400 drops below the present load, the output voltageof amplifier 416 will integrate downward until it becomes a negativevalue again thereby allowing the output of amplifier 418 to be directlyresponsive to movements in pedal 414.

As previously stated, it should be apparent to one skilled in the artthat the function of position sensor 402 can be performed by severaldifferent types of sensors without departing from the spirit and scopeof the invention. Furthermore, the description of circuits which willperform the comparator function and the voltage limiting function aremeant to be purely illustrative and not determinative of the invention.Also, the load on electric motor 400 can be sensed by any number ofcurrent sensors available in the art.

Referring to FIG. 14, shown therein is another embodiment of the presentinvention. Elements in this embodiment of the present invention that arecommon to the other embodiments are identified in FIG. 14 by the samereference numerals.

Referring to FIG. 14, the embodiment shown therein includes a primemover 450 having a drive shaft 12. Driving pulley FH which issubstantially the same as the driven pulley H previously described ismounted on drive shaft 12. Driving pulley FH is coupled to driven pulleyHF by V-belt 462. Driven pulley HF is substantially the same as thedriving pulley F previously described. Linear actuator X substantiallythe same as the linear actuators X₁ through X₃ previously described iscoupled to second pulley half F₂ of driven pulley HF. Speed sensor 452is coupled to driven pulley HF and the output of speed sensor 452 iscoupled to an input of comparator circuit 456. Reference level source454 is coupled to another input of comparator circuit 456 and the outputof comparator circuit 456 is coupled to the input of linear actuator X.

In practice, speed sensor 452 can be substantially the same as automaticsensind device L except that the dark nonreflecting areas may be ofconstant longitudinal width as shown in FIG. 15 instead of beingtriangular. It is understood that the particular pattern shown is asimplified schematic form and other forms and shapes may be desirable.Also, comparator circuit 456 can be substantially the same as thatportion of the electronic circuit of FIG. 9 comprising the seriesconnection of preamp 138, Schmidt trigger 140, monostable multivibrator142, low pass filter 144, summer 158 and power buffer 160 except thatreference level 454 is applied to the summer on conductor 164.Furthermore, the reference level 454 can comprise a source of directcurrent voltage represented by battery 460 coupled to a rheostat 458.

In operation, driving shaft 12 is rotated by prime mover 450. For thesake of illustration assume that the output rotational speed of primemover 450 is not a constant and varies over some range. The varyingrotational rate of prime mover 450 is transmitted via shaft 12, drivingpulley FH and V-belt 462 to driven pulley HF. The rotational speed ofdriven pulley HF is sensed by speed sensor 452 which generates an outputto comparator circuit 456. Comparator circuit 456 compares the outputfrom speed sensor 452 with a reference level 454. If the output fromspeed sensor 452 and the reference level are not equal, comparatorcircuit 456 delivers an output to energize actuator X to move the secondhalf F-2 of driven pulley HF to vary the effective pitch diameter ratiosof the driving and driven pulleys at FH and HF until the output of speedsensor 452 and the reference level are equal. Accordingly, so long asthe output from speed sensor 452 and the reference level 454 are equal,the speed of rotation of driven pulley HF is a constant irregardless ofthe changes in rotational speed of the driving pulley FH.

A specific embodiment of the linear actuator that may be employed withthe system of FIG. 9 is shown in FIGS. 16 and 17 showing a housing 500which encloses the pulley 502 comprising a movable pulley half 504 and afixed pulley half 506. The fixed pulley half 506 is mounted to be drivendirectly by the output 542 of the prime mover (e.g., output of theinternal combustion engine, electric motor, etc.). The fixed pulley half506 is thus fixed longitudinally with respect to movable pulley half 504which is adapted to slide longitudinally (arrows 508) with respect tofixed pulley half 506. The fixed pulley half 506 contains a bearinginsert 510 fixedly secured in an opening 512 in movable pulley half 504.The bearing 510 has a configuration as shown in FIG. 17 comprising aplurality of splinelike members which slidingly engage a mating hub 514,which hub portion has a matching male cross-section to matchingly engagethe bearing 510. Thus, it can be seen that the movable pulley half 504is free to slide in the direction of arrows 508 via bearing 510 on themating spline members 514 of the fixed half of the pulley 506.

The movable pulley half 504 has an internal lip 515 against which thebearing 510 abuts. The lip 515 also receives a washer 516 which washeris adapted to slidingly fit within the bore 517 of movable pulley half504. The washer 516 extends beyond lip 515 to engage the end of bearing514 in fixed pulley half 506. The coil spring 518 abuts the surface ofthe washer 516 and extends from the washer 516 to plate 528 which issecured to one end of the movable pulley half 504 by fastening means523. It can be seen that movement of the movable pulley half 504 in thedirection of arrows 508 toward the fixed pulley half 506 will result inthe spring 518 being compressed between washer 516 (fixed by the end ofspline 514) and plate 528 (which moves with movable pulley half 504).

The plate 528 has fixed therein a circulating ballnut 522 which is astandard commercially available component. The ballnut 522 receives leadscrew 520 which is secured to disc 534 which in turn is rotatablymounted in rotary bearing 536 by fastening means 538 (schematicallyshown). The lead screw 520 is also rotatably mounted at its end 548 inan opening 546 in the end of fastening means 540. The fastening means540 secures the fixed half of the pulley 506 of the prime mover outputshaft as schematically indicated as 542. Thus, it can be seen that leadscrew 520 is mounted for rotation so that it can rotate at the samespeed as ballnut 522 and movable pulley half 504 which rotate as a unitor lead screw 520 may rotate at a different speed with respect to saidballnut and movable pulley half 504. When a differential in speed existsbetween the lead screw and the movable half of pulley 504, the ballnutwill be displaced along the lead screw resulting in the movement ofmovable half pulley 504 and the compression of spring 518.

The disc 534 which is secured to lead screw 520 forms part of an eddycurrent brake 530. The eddy current brake includes a plurality of coils532 spaced around disc 534. Thus, the coils of eddy current brake 530may be energized to effect the force supplied to the disc 534 which inturn places a variable force on the lead screw that determines the speedof the lead screw with respect to ballnut 522.

A light and dark area sleeve 525 is mounted on the movable pulley half504 and fixed thereon by snap ring 526. The light and dark area sleevehas been previously described in connection with FIGS. 4 and 9. Thelight and dark areas on sleeve 525 cooperate with light sensor 529 andelectronic assembly 531 to provide position and RPM information as tomovable pulley half 504.

In summary, the above described linear actuator operates to change thepitch of the pulley by movement of the movable pulley half 504 withrespect to the fixed half 506. This movement is accomplished by therelative speed of the lead screw 520 with respect to the ballnut 522 andmovable pulley half 504 which rotates as a unit. The speed of the leadscrew is determined by the eddy current brake 530 as controlled by theelectronics hereinabove explained with the speed and positionalinformation of the movable half 504 determined by the light sensor 529and electronics 531 as explained in detail above.

One additional specific novel aspect of the above-described embodimentis the configuration of the spline 514 and the mating bearing 510 shownin detail in FIG. 17. It should be noted that the portions 511 of splineshaft 514 contact the belt 550. The configuration of portions 511 aresuch as to cause minimum wear of the belt 550. In addition, these splinemembers contact and drive the bearing of movable half 504 of the pulley.The depth of grooves 513 are less than three-eights of an inch andpreferably the wall 519 is approximately one-quarter of an inch. Thisminimizes metal removal while maintaining the strength of the shaft andbearing. Both the configuration and the fact that there are pluralitiesof such spline members enables the movable half 504 to be efficientlyand effectively drive by spline 514. Thus, the spline and bearingmembers present an additional novel aspect of this invention.

In all cases, it is understood that the above-described embodiments aremerely illustrative of but a small number of the many possible specificembodiments which can represent application of the principles of thepresent invention. Numerous and varied other arrangements can be readilydevised in accordance with these principles by those skilled in the artwithout departing from the spirit and scope of the invention.

I claim:
 1. A power drive assembly comprising:an endless V-belt; arotatably supported first shaft; a rotatably supported second shaftspaced from said first shaft and parallel thereto; a first pulleydefined by first and second halves, said first half being rigidlysecured to said first shaft and said second half being slideably mountedon said first shaft but nonrotatable relative thereto; a second pulleydefined by first and second halves, said first half of said secondpulley rigidly secured to said second shaft, and said second half ofsaid second pulley slideably mounted on said second shaft and slideablynonrotatable relative thereto; force exerting means that tends tomaintain said second half of said second pulley in a position relativeto said first half thereof such that the effective pitch diameter ofsaid second pulley is a maximum; spring means that tends to move saidsecond half of said first pulley to a predetermined maximum spacingrelative to said first half thereof; a first means operativelyassociated with said spring means for moving said second half of saidfirst pulley relative to said first half thereof when said first meansis energized; and a second means for energizing said first means inaccordance with a predetermined relationship thereby varying theeffective pitch diameter ratio of said first pulley and said secondpulley relative to said V-belt, said second means comprising:third meansfor sensing the rotational speed of said first shaft, said third meansgenerating a first output whose magnitude is related to said rotationalspeed; fourth means for sensing the relative position of said secondhalf of said first pulley to said first half, said fourth meansgenerating a second output whose magnitude is related to said relativeposition; and fifth means for comparing the difference in the magnitudeof said first output and second output and generating a third output toenergize said first means to move said second half relative to saidfirst half to vary the effective pitch diameters of said first andsecond pulley until said first and second outputs are equal.
 2. Anassembly as defined in claim 1 in which said first means comprises:Areversible electric motor that is actuated when it receives said thirdoutput from said fifth means; a rotatably supported threaded rod that isrotated by said motor; sixth means that threadably engage said threadedrod and move longitudinally relative thereto as said threaded rodrotates; and seventh means for transmitting said longitudinal movementof said fifth means to said second half of said first pulley to vary thepitch diameter of the latter.
 3. An assembly as defined in claim 2 inwhich said fifth means is a rigid block that has a taped bore thereinthat engages said threaded rod.
 4. An assembly as definded in claim 3 inwhich said seventh means is a thrust bearing having first and secondindependently rotatable portions that transfer longitudinal movement ofsaid block relative to said threaded rod to said second half of saidfirst pulley.
 5. In combination with a prime mover having a drivingshaft to which rotation of power is transmitted by said prime mover inaccordance with a predetermined torque curve inherent to said primemover, a power drive assembly operatively associated with said primemover for delivering rotational power output that is related to saidtorque curve, which assembly comprises:an endless V-belt; a rotatablysupported driven shaft spaced from said driving shaft and parallelthereto; a driving pulley defined by first and second halves, with saidfirst half being rigidly secured to said driving shaft, and said secondhalf being slidably mounted on said driving shaft, but nonrotatablerelative thereto; a driven pulley defined by first and second halves,said first half of said pulley rigidly secured to said driven shaft, andsaid second half of said driven pulley slidably mounted on said drivenshaft and substantially nonrotatable relative thereto; force exertingmeans that tends to so maintain said second half of said driven pulleyin a position relative to said first half thereof that the effectivepitch diameter of said driven pulley is a maximum; spring means thattends to move said second half of said driving pulley to a predeterminedmaximum spacing relative to said first half thereof; first meansoperatively associated with said spring means for moving said secondhalf of said driving pulley relative to said first half thereof whensaid first means is energized; second means for sensing the rotationalspeed of said driving shaft, said second means generating a first outputwhose magnitude is related to said rotational speed; third means forsensing the relative position of said second half of said driving pulleyto said first half, said third means generating a second output whosemagnitude is related to said relative position; and fourth means forcomparing the difference in the magnitudes of said first output and saidsecond output and generating a third output to energize said first meansto move said second half of said driving pulley relative to said firsthalf to vary the effective pitch diameters of said driving and drivenpulleys until said first and second outputs are equal whereupon saidprime mover operates in a desired relation to said torque curve indelivering torque to said driven pulley.
 6. A power drive assemblyaccording to claim 5 wherein said second, third and fourth meanscomprise:endless surface defining means that occupy a fixed positionrelative to said second half of said driving pulley and rotateconcurrently therewith; a plurality of circumferentially spaced,elongate light reflecting areas defined on said endless surface definingmeans, with each of said areas varying longitudinally in width; meansfor directing a stationery, continuous first beam of light onto saidareas to be reflected therefrom as a second beam of intermittent pulseswhich vary in frequency and duration in accordance with the speed ofrotation of said driving pulley and the position of said areaslongitudinally relative to said first beam; a source of electric power;and an electronic circuit energized by said source of electric power,which circuit includes a phototransistor on which said second beamimpinges to render the same conductive, with said circuit includingfirst and second portions that receive pulses of electric energy fromsaid phototransistor and transform the same into first and secondvoltages that correspond in magnitude to the rate at which said areasmove past said first beam of light and the duration of time of each ofsaid pulses of said second beam of light, with said circuit alsoincluding first means for comparing the difference in magnitude betweensaid first and second voltages, and second means responsive to saiddifference for energizing said first means to move said second half ofsaid driving pulley relative to said first half to vary the effectivepitch diameters of said driving and driven pulleys until said first andsecond voltages are equal whereupon said prime mover operates in adesired relationship to said torque curve in delivering torque to saiddriven pulley.
 7. An assembly as defined in claim 6 in which said forceexerting means is a compression helical spring that encircles saiddriven shaft, with said spring having first and second ends, with saidfirst end being in a fixed position relative to said shaft and saidsecond end being in force exerting contact with said second half of saiddriven pulley.
 8. An assembly as defined in claim 7 in which saidendless surface defining means is cylindrical in shape and said lightreflecting areas defined therein are generally triangular inconfiguration.
 9. An assembly as defined in claim 6 in which said firstmeans comprises:a reversible electric motor that is actuated when itreceives electric power from said second portions of said electriccircuit; a rotatably supported threaded rod that is rotated by saidmotor; fifth means that threadably engage said threaded rod and movelongitudinally relative thereto as said threaded rod rotates; and sixthmeans for transmitting said longitudinal movement of said fifth means tosaid second half of said driving pulley to vary the pitch diameter ofthe latter.
 10. An assembly as defined in claim 9 in which said fifthmeans is a rigid block that has a tapped bore therein that engages saidthreaded rod.
 11. An assembly as defined in claim 10 in which said sixthmeans is a thrust bearing having first and second independentlyrotatable portions that transfer longitudinal movement of said blockrelative to said threaded rod to said second half of said drivingpulley.
 12. An assembly as defined in claim 6 in which said firstportion of said electric circuit includes a preamplifier, a Schmidttrigger, a monostable multivibrator and a low pass filter in series withsaid first voltage flowing to said first means.
 13. An assembly asdefined in claim 6 in which said second portion of said electric circuitincludes a low pass filter, an inverter and summer that are connected ina series with said low pass filter being connected to the output of suchSchmidt trigger, and said second portion delivering said second voltageto said first means.
 14. An assembly as defined in claim 6 in which saidfirst means comprises:a reversible electric motor; a threaded rodrotated by said motor; first and second hydraulic fluid containingcylinders that occupy fixed positions relative to said engine, saidcylinder including first end portions connected by a fluid passageway;first and second pistons slidably and sealably mounted in said first andsecond cylinders with said second piston having a tapped bore thereinthat threadably engages with said threaded rod; and bearing meansdisposed between said first piston and said second half of said drivingpulley for moving said second half of said driving pulley relative tosaid first half thereof to vary the pitch diameter of said drivingpulley when hydraulic fluid flows into and out of said cylinder throughsaid fluid passage due to said electric motor being energized to movesaid said second piston in said cylinder to vary the quantity of saidhydraulic fluid in said first cylinder.
 15. An assembly as defined inclaim 6 in which said first means comprises:a threaded rod that extendsoutwardly from said second half of said driving pulley and rotatesconcurrently therewith; a hysteresis brake that includes a stationaryouter portion containing electrical coils and an inner portion thatrotates freely relative to said outer portion except when said coils areelectrically energized, said inner portion having a longitudinal boretherein through which said threaded rod extends; and a nut on said innerportion that is longitudinally aligned with said bore and engaged bysaid rod, with said rod rotating relative to said nut when said coilsare energized to stop the rotation of said inner portion, and saidsecond half of said driving pulley being moved laterally relative tosaid first half as a result thereof.
 16. An assembly as in claim 6 inwhich said prime mover comprises an internal combustion engine.
 17. Incombination with an internal combustion engine having a driving shaft towhich rotational power is transmitted by said engine in accordance witha predetermined torque curve inherent to said engine, a power driveassembly operatively associated with said engine for delivering arotational power output that is related to said torque curve, whichassembly includes:an endless V-belt; a rotatably supported driven shaftspaced from said driving shaft and parallel thereto; a driving pulleydefined by first and second halves, with said first half being rigidlysecured to said driving shaft, and said second half being slidablymounted on said driving shaft but non-rotatable relative thereto; adriven pulley defined by first and second halves, said first half ofsaid driven pulley rigidly secured to said driven shaft, and said secondhalf of said driven pulley slidably mounted on said driven shaft andsubstantially non-rotatable relative thereto; force-exerting means thattends to so maintain said second half of said driven pulley in aposition relative to said first half thereof that the effective pitchdiameter of said driven pulley is maximum; spring means that tends tomove said second half of said driving pulley to a predetermined maximumspacing relative to said first half thereof; endless surface-definingmeans that occupy a fixed position relative to said second half of saiddriving pulley and rotate concurrently therewith; a plurality ofcircumferentially spaced, elongate light-reflecting areas defined onsaid endless surface defining means, with each of said areas varyinglongitudinally in width; means for directing a continuous first beam oflight onto said areas to be reflected therefrom as a second beam ofintermittent pulses which vary in frequency and duration in accordancewith the speed of rotation of said driving pulley and the position ofsaid areas longitudinally relative to said first beam; a source ofelectric power; electric power-operated means operatively associatedwith said spring means for moving said second half of said drivingpulley relative to said first half thereof when said power operatedmeans is electrically energized to vary the effective pitch diameter ofsaid driving pulley, and the effective pitch diameter of said drivenpulley varying in response to variation of the tension on said belt asthe effective pitch diameter of said driving pulley varies; and anelectronic circuit energized by said source of electric power, whichcircuit includes a phototransistor on which said second beam impinges torender the same conductive, with said circuit including first and secondportions that receive pulses of electric energy from saidphototransistor and transform the same into first and second voltagesthat correspond in magnitude to the rate at which said areas move pastsaid first beam of light and the duration of time of each of said pulsesof said second beam of light, with said circuit also including firstmeans for comparing the difference in magnitude between said first andsecond voltages, and second means responsive to said difference fordelivering electric power to said electric power-operated means to movesaid second half relative to said first half to vary the effective pitchdiameters of said driving and driven pulley until said first and secondvoltages are equal whereupon said engine operates in a desiredrelationship to said torque curve in delivering torque to said drivenpulley.
 18. An assembly as defined in claim 17 in which saidforce-exerting means is a compressed helical spring that encircles saiddriven shaft, with said spring having first and second ends, with saidfirst end being in a fixed position relative to said shaft and saidsecond end being in force-exerting contact with said half of said drivenpulley.
 19. An assembly as defined in claim 17 in which said endlesssurface defining means is cylindrical in shape and said light reflectingareas defined thereon are generally triangular in configuration.
 20. Anassembly as defined in claim 17 in which said surface-defining means isan endless flat band and said light reflecting areas defined thereon aregenerally triangular in configuration.
 21. An assembly as defined inclaim 17 in which said power operated means includes:a reversibleelectric motor that is actuated when it receives electric power fromsaid second means; a rotatably supported threaded rod that is rotated bysaid motor; third means that threadably engage said threaded rod andmove longitudinally relative thereto as said threaded rod rotates; andfourth means for transmitting said longitudinal movement of said thirdmeans to said second half of said driving pulley to vary the pitchdiameter of the latter.
 22. An assembly as defined in claim 21 in whichsaid third means is a rigid block that has a tapped bore therein thatengages said threaded rod.
 23. An assembly as defined in claim 21 inwhich said fourth means is a bearing having first and secondindependently rotatable portions that transfer longitudinal movement ofsaid block relative to said threaded rod to said second half of saiddriving pulley.
 24. An assembly as defined in claim 17 in which saidfirst portion of said electric circuit includes a preamplifier, aSchmidt trigger, monostable multivibrator and a low pass filter inseries, with said first voltage flowing to said first means.
 25. Anassembly as defined in claim 17 in which said second portion includes alow pass filter, an inverter and a summer that are connected in serieswith said low pass filter being connected to the output of said Schmidttrigger, and said second portion delivering said second voltage to saidfirst means.
 26. An assembly as defined in claim 17 in which said poweroperated means includes:a reversible electric motor; a threaded rodrotated by said motor; first and second hydraulic fluid containingcylinders that occupy fixed positions relative to said engine, saidcylinder including first end portions connected by a fluid passage;first and second pistons slidably and sealingly mounted in said firstand second cylinders with said second piston having a tapped boretherein that threadably engages said threaded rod; and bearing meansdisposed between said first piston and said second half of said drivingpulley for moving said second half of said driving pulley relative tosaid first half thereof to vary the pitch diameter of said drivingpulley when hydraulic fluid flows into and out of said cylinder throughsaid fluid passage due to said electric motor being energized to movesaid second piston in said cylinder to vary the quantity of saidhydraulic fluid in said first cylinder.
 27. An assembly as defined inclaim 17 in which said electric power operated means includes:a threadedrod that extends outwardly from said second half of said driving pulleyand rotates concurrently therewith; a hysteresis brake that includes astationary outer portion containing electrical coils and an innerportion that rotates freely relative to said outer portion except whensaid coils are electrically energized, said inner portion having alongitudinal bore therein through which said threaded rod extends; and anut on said inner portion that is longitudinally aligned with said boreand engaged by said rod, with said rod rotating relative to said nutwhen said coils are energized to stop the rotation of said innerportion, and said second half of said driving pulley being movedlaterally relative to said first half as a result thereof.